This invention relates generally to non-contacting heat exchangers and more particularly to a double wall tube assembly which defines fluid flow passages for non-contacting heat exchangers to meet local code requirements for preventing contamination of at least one of the fluids in the fluid flow passages such as potable water.
The present invention is particularly applicable for energy conservation wherein waste heat is recovered or reclaimed from refrigerant circuits or systems.
It is well known to put a desuperheater i.e., a non-contacting heat exchanger in the hot gas discharge line from the discharge outlet for the compressor in a refrigeration circuit or system in order to recover the waste heat from the hot compressed refrigerant gases discharged by the compressor.
Heretofore prior art desuperheaters included, tube assemblies consisting of two parallel flow passages in which potable water was passed through one passage and hot compressed refrigerant gas was passed through the other passage to permit the potable water to reclaim or recover the waste heat from the hot compressed refrigerant gas.
Such prior art tube assemblies consisted of two concentric tubes generally termed tube within a tube assemblies so that only a single heat conducting wall existed between the parallel flow passages. If this single wall failed the respective fluids passing through the parallel flow passages would contaminate each other. This was particularly important in the case where potable water was one of the fluids passing through the parallel flow passages.
Accordingly, the National Bureau of Standards and the Department of Housing and Urban Development have now established federal regulations which require double walls in heat exchange equipment where potable water is one of the fluids passing in heat exchange relation with hot compressed refrigerant gases for recovering or reclaiming heat therefrom.
These regulations have been adopted in local codes throughout the United States.
These regulations and codes respecting potable water pose difficulties on heat exchanger efficiency and characteristics because they require a departure from the known tube within a tube assemblies in that the thickness of the conductive walls of the tube assemblies is now doubled and the presence of air or other materials between the respective walls for such double wall tube assemblies as is known to those skilled in the art decreases heat exchange efficiency.
The present invention provides an improved double wall tube assembly in accordance with the requirements of the new regulations which can meet the local codes now imposed on refrigerant to liquid heat exchangers by shaping and sizing at least one of the tubes to permit intimate operative connection on at least two sides of such tube with an adjacent tube or tubes so that optimum heat exchange relation and efficiency is established for the heat exchanger when used as a desuperheater in such refrigerant circuits or systems.